Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary:

# Callback

` public interface Callback `   
` `

|---|
| javax.security.auth.callback.Callback |

Known indirect subclasses [PasswordCallback](https://developer.android.com/reference/javax/security/auth/callback/PasswordCallback) [PasswordCallback](https://developer.android.com/reference/javax/security/auth/callback/PasswordCallback) Underlying security services instantiate and pass a `PasswordCallback` to the `handle` method of a `CallbackHandler` to retrieve password information.

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Implementations of this interface are passed to a `CallbackHandler`, allowing underlying security services the ability to interact with a calling application to retrieve specific authentication data such as usernames and passwords, or to display certain information, such as error and warning messages.

`Callback` implementations do not retrieve or display the information requested by underlying security services. `Callback` implementations simply provide the means to pass such requests to applications, and for applications, if appropriate, to return requested information back to the underlying security services.
**See also:**

- `https://developer.android.com/reference/javax/security/auth/callback/CallbackHandler`
- `https://developer.android.com/reference/javax/security/auth/callback/PasswordCallback`